/* Copyright  2009
   @Author
   Richard Changde Yin            e-mail yinchangde@hotmail.com

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/**
 * @filename: ha_trx_info.h
 */

#ifndef __HA_TRX_INFO_H__
#define __HA_TRX_INFO_H__


class Session_TRANS;

/**
  Either statement transaction or normal transaction - related
  thread-specific storage engine data.

  If a storage engine participates in a statement/transaction,
  an instance of this class is present in
  session->transaction.{stmt|all}.ha_list. The addition to
  {stmt|all}.ha_list is made by trans_register_ha().

  When it's time to commit or rollback, each element of ha_list
  is used to access storage engine's prepare()/commit()/rollback()
  methods, and also to evaluate if a full two phase commit is
  necessary.

  @sa General description of transaction handling in handler.cc.
*/

class Ha_trx_info
{
public:
  /** Register this storage engine in the given transaction context. */
  void register_ha(Session_TRANS *trans);


  /** Clear, prepare for reuse. */
  void reset();
  Ha_trx_info() { reset(); }

  void set_trx_read_write();
  bool is_trx_read_write() const;
  bool is_started()        const;

  /** Mark this transaction read-write if the argument is read-write. */
  void coalesce_trx_with(const Ha_trx_info *stmt_trx);
  Ha_trx_info *next() const;

private:
  enum { TRX_READ_ONLY= 0,
         TRX_READ_WRITE= 1
       };
  /** Auxiliary, used for ha_list management */
  Ha_trx_info *m_next;
  /**
    Transaction flags related to this engine.
    Not-null only if this instance is a part of transaction.
    May assume a combination of enum values above.
  */
  unsigned char       m_flags;
};

#endif /* __HA_TRX_INFO_H__ */
